In building construction, electrical boxes for wall-mounted devices, such as duplex receptacles or switches, are usually installed by the electrical contractor prior to the finishing of the walls. Since the wall finishing has not yet been installed at the time of the electrical work, the electrical contractor must anticipate the level of the finished wall and install the electrical boxes such that the front edge is at the desired offset from the finished wall. With the current state of the art, the electrical contractor must therefore measure during the installation of each separate electrical box to insure that the box is positioned at the correct offset with respect to the wall.
In construction of stucco walls, the wall studs are typically covered with plywood and then with foam. The foam thickness can be ½, ¾, 1″, etc., depending on the weather in the area it's being installed in and depending on the local requirements. For example, for installation of a covered electrical box for a duplex outlet, if the local code calls for 1″ of foam and ¼″ of stucco, then the contractor must typically allow 1¼″ for the thickness of foam and stucco plus ½ for the front of the box to extend beyond the wall surface to allow the cover to open and close. This allows the electrical contractor to install the box on the unfinished wall and complete the electrical work ahead of the finishing contractor. With current state of the art electrical boxes for wall-mounted devices, the electrical contractor must measure the location of each electrical box with respect to the wall before securing the box in place.
A further problem with prior art electrical boxes arises from the fastening arrangement for securing to the wall. Prior art boxes typically have nails or screws set an angle to the front edge of the box and they typically tend to shift the box as the fasteners are hammered or screwed into the studs. Thus, even if the installer has measured for the correct offset from the wall, the fastening arrangement may shift the box away from the desired offset.
It should be apparent from the above discussion that installation of prior art electrical boxes is a time-consuming task that does not always result in an electrical box being positioned correctly with respect to the wall's surface. What is needed therefore is a device that reduces the time and effort involved in installing an electrical box at a desired offset from a wall's outer surface. The device must also include a fastening arrangement that does not cause shifting of the box as the box is secured to the framing members.